1. Field of the Disclosure
The present disclosure relates generally to device packaging, and more particularly to three-dimensional (3D) stacked die packaging.
2. Description of the Related Art
Electronic devices often utilize three-dimensional (3D) integrated circuit (IC) packaging to stack two or more dice in a package, which provides a smaller footprint compared to a single larger die or two side-by-side dice connected via an interposer. A common 3D packaging approach for stacking two dice employs a pillar-to-pillar die stacking technique wherein copper pillars are formed on each die and the two dice are then bonded such that each pillar on one die aligns with, and comes into contact with, a corresponding pillar on the other die so as to form a mechanical and electrical bond. However, the copper pillars must be aligned with precision; if one die is angled relative to the other, or the copper pillar bumps are otherwise misaligned, they may not wet (i.e. electrically and mechanically bond). In an attempt to prevent non-wetting, many non-electrically active pillars are added to the dice, increasing the footprint of the technique. Moreover, this pillar-to-pillar die stacking technique creates a large void, or standoff, between the two dice that requires underfill, as well as dams to prevent lateral disbursement of the underfill.